{{note|1= With {{pkg|shadow}} 4.1.4.3-3 ''sha512'' is the default for new passwords (see [https://bugs.archlinux.org/task/13591#comment85993 bug 13591] and corresponding [http://projects.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/shadow&id=98001501a8306ef5a0df55d1cffc048851894940 commit]).}}

+

{{note|1= With {{pkg|shadow}} 4.1.4.3-3 ''sha512'' is the default for new passwords (see [https://bugs.archlinux.org/task/13591#comment85993 bug 13591] and corresponding [https://projects.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/shadow&id=98001501a8306ef5a0df55d1cffc048851894940 commit]).}}

−

If you are encrypting your whole home, with auto-mounting you should use a strong password and consider changing the hash algorithm for ''/etc/shadow''. From '''md5''' to stronger ones like '''sha512/bcrypt''', that helps to protect your password against rainbow-table attacks. See https://wiki.archlinux.org/index.php/SHA_password_hashes for more information.

+

If you are encrypting your whole home, with auto-mounting you should use a strong password and consider changing the hash algorithm for ''/etc/shadow'' from '''md5''' to stronger ones like '''sha512/bcrypt''' that helps to protect your password against rainbow-table attacks. See https://wiki.archlinux.org/index.php/SHA_password_hashes for more information.

== Basics ==

== Basics ==

Line 82:

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* The signature of the key(s) will be stored in {{ic|/root/.ecryptfs/sig-cache.txt}}.

* The signature of the key(s) will be stored in {{ic|/root/.ecryptfs/sig-cache.txt}}.

−

Since our later goal is to be able to mount without root priviledges, we will now move the eCryptfs configuration directory to your own home and transfer the ownership to you:

+

Since our later goal is to be able to mount without root privileges, we will now move the eCryptfs configuration directory to your own home and transfer the ownership to you:

# mv /root/.ecryptfs /home/username

# mv /root/.ecryptfs /home/username

# chown username:username /home/username/.ecryptfs

# chown username:username /home/username/.ecryptfs

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=== Mounting (the hard way) ===

=== Mounting (the hard way) ===

−

When ever you need your files available you can repeat the above mount procedure, using the same passphrase and options if you want to access your previously encrypted files or using a different passphrase (and possibly options) if for some reason you want to have different keys protecting different data (imagine having a publicly shared directory where different data is encrypted by different users, and their keys).

+

Whenever you need your files available you can repeat the above mount procedure, using the same passphrase and options if you want to access your previously encrypted files or using a different passphrase (and possibly options) if for some reason you want to have different keys protecting different data (imagine having a publicly shared directory where different data is encrypted by different users, and their keys).

In any case going trough those questions every time could be a bit tedious.

In any case going trough those questions every time could be a bit tedious.

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One solution would be to create an entry in the '''{{ic|/etc/fstab}}''' file for this mount point:

One solution would be to create an entry in the '''{{ic|/etc/fstab}}''' file for this mount point:

* You will notice that we defined the '''user''' option, it enables you to mount the directory as a user (if it does not works as a normal user, you may need to setuid mount.ecryptfs by running as root: ''chmod +s /sbin/mount.ecryptfs'')

* You will notice that we defined the '''user''' option, it enables you to mount the directory as a user (if it does not works as a normal user, you may need to setuid mount.ecryptfs by running as root: ''chmod +s /sbin/mount.ecryptfs'')

2) Install [http://www.archlinux.org/packages/core/x86_64/keyutils/ keyutils] and [http://www.archlinux.org/packages/community/x86_64/ecryptfs-utils/ ecryptfs-utils] from the official Repos.

+

2) Install [https://www.archlinux.org/packages/core/x86_64/keyutils/ keyutils] and [https://www.archlinux.org/packages/community/x86_64/ecryptfs-utils/ ecryptfs-utils] from the official Repos.

'''[Do the following steps as root!]'''

'''[Do the following steps as root!]'''

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'''password optional pam_ecryptfs.so'''

'''password optional pam_ecryptfs.so'''

−

ge) For [[LightDM]], make the following changes to /etc/pam.d/lightdm

+

6e) For [[LightDM]], make the following changes to /etc/pam.d/lightdm

#%PAM-1.0

#%PAM-1.0

auth required pam_nologin.so

auth required pam_nologin.so

auth required pam_env.so

auth required pam_env.so

+

auth required pam_unix.so

'''auth optional pam_ecryptfs.so unwrap'''

'''auth optional pam_ecryptfs.so unwrap'''

−

auth required pam_unix.so

account required pam_unix.so

account required pam_unix.so

−

'''password optional pam_ecryptfs.so unwrap'''

+

'''password optional pam_ecryptfs.so'''

password required pam_unix.so

password required pam_unix.so

session required pam_unix.so

session required pam_unix.so

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Line 349:

Besides this, it has the advantage of auto-unmount at log-out, which shell profile files (ie. ~/.bash_logout) could have trouble doing, because there could still be open file-descriptors by the shell at the time of umount. To encrypt swap see: [[System_Encryption_with_LUKS#Encrypting_the_Swap_partition]] (some of the tools provided by ecryptfs, such as ecryptfs-setup-swap, only work in ubuntu).

Besides this, it has the advantage of auto-unmount at log-out, which shell profile files (ie. ~/.bash_logout) could have trouble doing, because there could still be open file-descriptors by the shell at the time of umount. To encrypt swap see: [[System_Encryption_with_LUKS#Encrypting_the_Swap_partition]] (some of the tools provided by ecryptfs, such as ecryptfs-setup-swap, only work in ubuntu).

−

== Simple ==

+

== ecryptfs-simple ==

Use [http://xyne.archlinux.ca/projects/ecryptfs-simple/ ecryptfs-simple] if you just want to use eCryptfs to mount arbitrary directories the way you can with EncFS. ecryptfs-simple does not require root privileges or entries in fstab, nor is it limited to hard-coded directories such as ~/.Private. The package is available in the [https://aur.archlinux.org/packages.php?ID=59612 AUR] and in [http://xyne.archlinux.ca/repos/ Xyne's repos].

Use [http://xyne.archlinux.ca/projects/ecryptfs-simple/ ecryptfs-simple] if you just want to use eCryptfs to mount arbitrary directories the way you can with EncFS. ecryptfs-simple does not require root privileges or entries in fstab, nor is it limited to hard-coded directories such as ~/.Private. The package is available in the [https://aur.archlinux.org/packages.php?ID=59612 AUR] and in [http://xyne.archlinux.ca/repos/ Xyne's repos].

Revision as of 06:11, 2 January 2013

This article describes basic usage of eCryptfs. It guides you through the process of creating a private and secure encrypted directory within your $HOME directory, where you can store all your sensitive files and private data.

In implementation eCryptfs differs from dm-crypt, which provides a block device encryption layer, while eCryptfs is an actual file-system – a stacked cryptographic file system to be exact. For comparison of the two you can refer to this table .

The summary is that it doesn't require special on-disk storage allocation effort, such as separate partitions, you can mount eCryptfs on top of any single directory to protect it. That includes e.g. your entire $HOME and network file systems (i.e. having encrypted NFS shares). All cryptographic metadata is stored in the headers of files, so encrypted data can be easily moved, stored for backup and recovered. There are other advantages, but there are also drawbacks, for instance eCryptfs is not suitable for encrypting complete partitions which also means you can't protect your swap space with it (instead you can combine it with dm-crypt).

Deficiencies

Before you make any big decisions like encrypting your $HOME you should know that eCyptfs does not handle sparse files well. For most intents and purposes that shouldn't concern us, however one very popular use case are torrents. Right now eCryptfs tries to encrypt the whole sparse file allocated space right away, which can lead to starving the system of resources in case of big files (remember torrents can easily be 10GB or bigger). You can track progress of this bug in this Launchpad report: https://bugs.launchpad.net/ubuntu/+source/ecryptfs-utils/+bug/431975

Simple workaround, for now, is to create a .Public folder (as .Private folder is used for encrypted data later in the article) and use that for torrents, unencrypted and symlinked to a directory like ~/Downloads/torrents. For some people this of course defeats the whole purpose of encryption, for others who are protecting their data from theft it doesn't.

Login password

Note: With shadow 4.1.4.3-3 sha512 is the default for new passwords (see bug 13591 and corresponding commit).

If you are encrypting your whole home, with auto-mounting you should use a strong password and consider changing the hash algorithm for /etc/shadow from md5 to stronger ones like sha512/bcrypt that helps to protect your password against rainbow-table attacks. See https://wiki.archlinux.org/index.php/SHA_password_hashes for more information.

Basics

eCryptfs is a part of Linux since version 2.6.19. But to work with it you will need the userspace tools provided by the package ecryptfs-utils available in the Official Repositories.

Once you have installed that package you can load the ecryptfs module and continue with the setup:

# modprobe ecryptfs

The ecryptfs-utils package is distributed with a few helper scripts which will help you with key management and similar tasks. Some were written to automate this whole process of setting up encrypted directories (ecryptfs-setup-private) or help you combine eCryptfs with dm-crypt to protect swap space (ecryptfs-setup-swap). Despite those scripts we will go trough the process manually so you get a better understanding of what is really being done.

Before we say anything else it's advised that you check the eCryptfs documentation. It is distributed with a very good and complete set of manual pages.

Setup (simple)

As a user run

ecryptfs-setup-private

and follow the instructions.

Setup (in detail)

First create your private directories, in this example we will call them exactly that: Private

While mounted, decrypted data will be available in ~/Private directory (so-called upper directory)

While not mounted nothing can be written to this directory

While mounted it has the same permissions as the lower directory

eCryptfs can now be mounted on top of ~/Private.

# mount -t ecryptfs /home/username/.Private /home/username/Private

You will need to answer a few questions and provide a passphrase which should be used to mount this directory in the future. However you can also have different keys encrypting different data (more about this below). For convenience we will limit this guide to only one key and passphrase. Let's see an example:

Your setup is now complete and directory is mounted. You can place any file in the ~/Private directory and it will get encrypted in ~/.Private.

Now copy a few files to your new private directory, and then un-mount it. If you inspect the files you will see that they are unreadable – encrypted. That was cool you say, but how do I get them back... and that brings us to:

Extra Notes

Above is detailed the simplest way to setup the mount point, but ecryptfs-setup-private runs through some extra steps.

The above mount passphrase is derived from the passphrase you type in. This is not considered very secure, so the setup script grabs some characters from /dev/random for safety:

Mounting (the hard way)

Whenever you need your files available you can repeat the above mount procedure, using the same passphrase and options if you want to access your previously encrypted files or using a different passphrase (and possibly options) if for some reason you want to have different keys protecting different data (imagine having a publicly shared directory where different data is encrypted by different users, and their keys).

In any case going trough those questions every time could be a bit tedious.

One solution would be to create an entry in the /etc/fstab file for this mount point:

You will notice that we defined the user option, it enables you to mount the directory as a user (if it does not works as a normal user, you may need to setuid mount.ecryptfs by running as root: chmod +s /sbin/mount.ecryptfs)

Notice the ecryptfs_sig option, replace XY with your own key signature (as seen in the mtab line earlier and in sig-cache.txt)

If you enabled filename encryption then pass an additional mount option: ecryptfs_fnek_sig=XY, where XY is the same signature you provide with the ecryptfs_sig option.

Last option ecrypfs_unlink_sigs ensures that your keyring is cleared every time the directory is un-mounted

Since your key was deleted from the kernel keyring when you un-mounted, in order to mount you need to insert it into the keyring again. You can use the ecryptfs-add-passphrase utility or the ecryptfs-manager to do it:

You will notice that we used the -i option this time. It disables invoking the mount helper. Speaking of which, using -i by default mounts with: nosuid, noexec and nodev. If you want to have at least executable files in your private directory you can add the exec option to the fstab line.

This would be a good place to mention the keyctl utility from the (earlier installed) keyutils package. It can be used for any advanced key management tasks. Following examples show how to list your keyring contents and how to clear them:

$ keyctl list @u
$ keyctl clear @u

Note: However, one should remember that /etc/fstab is for system-wide partitions only and should not be used for user-specific mounts

Auto-mounting (the easy way)

A better way is to use PAM directly, see:

/usr/share/doc/ecryptfs-utils/README

1. Open /etc/pam.d/login and add

auth required pam_ecryptfs.so unwrap

after the line containing auth ... pam_unix.so, and

session optional pam_ecryptfs.so unwrap

after the line session ... pam_unix.so.

2. Check if ~/.ecryptfs/auto-mount and ~/.ecryptfs/wrapped-passphrase (these are automatically created by ecryptfs-setup-private) exist.

3. Relogin and check output of mount which should now contain a mountpoint

/home/user/.Private...

Usage

Besides using your private directory as storage for sensitive files, and private data, you can also use it to protect application data. Take Firefox for an example, not only does it have an internal password manager but the browsing history and cache can also be sensitive. Protecting it is easy:

Removal

If you want to move a file out of the private directory just move it to it's new destination while ~/Private is mounted. Also note that there are no special steps involved if you want to remove your private directory. Make sure it is un-mounted and delete ~/.Private, along with all the files.

Backup

Setup explained here separates the directory with encrypted data from the mount point, so the encrypted data is available for backup at any time. With an overlay mount (i.e. ~/Secret mounted over ~/Secret) the lower, encrypted, data is harder to get to. Today when cronjobs and other automation software do automatic backups the risk of leaking your sensitive data is higher.

We explained earlier that all cryptographic metadata is stored in the headers of files. You can easily do backups, or incremental backups, of your ~/.Private directory, treating it like any other directory.

Advanced

This wiki article covers only the basic setup of a private encrypted directory. There is however another article about eCryptfs on Arch Linux, which covers encryption of your entire $HOME and encrypting swap space without breaking hibernation (suspend to disk).

That article includes many more steps (i.e. using PAM modules and automatic mounting) and the author was opposed to replicating it here, because there is just no single "right" way to do it. The author proposes some solutions and discusses the security implications, but they are his solutions and as such might not be the best nor are they endorsed by the eCryptfs project in any way.

Consider that Chromium OS, as released by Google, is using eCryptfs to protect devices that are, and will be, powered by it. Some implementation details are available and they make excellent reading. You can read them here, they could help a lot as you're coming up with your own strategy.

PAM Mount

The above "eCryptfs and $HOME" article uses a shell init file to mount the home directory. The same can be done using pam_mount with the added benefit that home is un-mounted when all sessions are logged out. Add the following lines to /etc/security/pam_mount.conf.xml:

The article suggests adding these to /etc/pam.d/login, but the changes will need to be added to all other places you login, such as /etc/pam.d/kde.

PAM mount by eCryptfs module

To use the eCryptfs PAM module it self for mounting you should know it depends on some hard-coded Ubuntu defaults. Like using AES cipher with a 16 byte key. As described in this BBS post [1] you have to do the following steps:

This is a working solution and ecryptfs is exactly used as in Ubuntu (10.04/10.10) - and is easy to set up.
Besides this, it has the advantage of auto-unmount at log-out, which shell profile files (ie. ~/.bash_logout) could have trouble doing, because there could still be open file-descriptors by the shell at the time of umount. To encrypt swap see: System_Encryption_with_LUKS#Encrypting_the_Swap_partition (some of the tools provided by ecryptfs, such as ecryptfs-setup-swap, only work in ubuntu).

ecryptfs-simple

Use ecryptfs-simple if you just want to use eCryptfs to mount arbitrary directories the way you can with EncFS. ecryptfs-simple does not require root privileges or entries in fstab, nor is it limited to hard-coded directories such as ~/.Private. The package is available in the AUR and in Xyne's repos.

As the name implies, usage is simple:

# simple mounting
ecryptfs-simple /path/to/foo /path/to/bar

# automatic mounting: prompts for options on the first mount of a directory then reloads them next time
ecryptfs-simple -a /path/to/foo /path/to/bar